Health Secretary Patricia Hewitt has warned NHS managers they must renew efforts to meet a key cancer target by the end of the year.
The cancer targets should be met by the end of the year
The 2000 Cancer Plan promised patients would have to wait only two months from referral to treatment, and a month from diagnosis to treatment, by December.
But Ms Hewitt told health service bosses at a conference that progress has been slow on the two-month goal.
She urged them to show more focus in the next six months.
Part of the problem is long waits for lab test and scan results.
In an address to the National Cancer Waits conference in London, the health secretary said: "These are not targets for the sake of targets, they are targets for the sake of patients.
"The 31 and 62 day targets have been achieved for breast cancer and we've clearly seen how they are benefitting patients.
"They are being achieved for other cancers in some parts of the country. They must be achieved for all cancer patients in all parts of the country."
Mrs Hewitt said achievement of the targets was reliant on trusts working together to ensure patients who were diagnosed in one trust and treated in another were transferred quickly and efficiently.
"Nobody is denying that meeting these targets for all cancer patients will be tough.
"We have a collective responsibility to maintain this momentum of reform, at both a national and a local level, if every cancer patient is to recieve a service that compares with the best in the world."
The Department of Health is not revealing how many trusts are struggling to meet the target as the data is not available.
But official figures earlier this year suggested one in five patients were not being seen within the two-month target, and one in ten within the month target.
Only breast cancer services are thought to have made significant progress with more than 96% treated within two months of referral.
It is not the first time the NHS has been warned about the targets.
Cancer tsar Professor Mike Richards said in his report last year that the health service was facing an "enormous challenge".
And in March a King's Fund audit of Labour's health record said it was an "ambitious" target and would require further investment in staff and diagnostic procedure if it was to be met.
Patricia Hewitt visits the Breast Care Centre at Barts Hospital
CancerBACUP chief executive Joanne Rule agreed many areas were struggling.
"There are problems with both of them, but especially the two-month target.
"Diagnosis doesn't happen with just one test, so while the two-month wait incorporates all the different test, the other one does not start until the diagnosis has been made.
"Our surveys do not suggest there is a lack of resources, except maybe in a few areas, so we can still meet them.
"What we need now is for everyone involved to concentrate and work hard.
"These targets matter - in many other countries these waits would seem a long time."
Jola Gore-Booth, of the charity Colon Cancer Concern, said: "When the government's NHS Cancer Plan was introduced in July 2000, NHS waiting times for bowel cancer patients from referral to treatment stood at 3 months (92 days).
"They have now risen to over six months (201 days) - double the figure of five years ago.
"We have to be realistic when considering the reasons for these continuing delays.
"There is obviously a significant amount of pressure on the health system already and this can only be eased by an expansion in infrastructure."